The **UCAC3** star catalog was published by USNO at the end of august.\\

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The **UCAC3** star catalog was published by USNO at the end of august ​2009.\\

Its main characteristics are:

Its main characteristics are:

* Full sky coverage

* Full sky coverage

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* Imprecise or missing bright stars

* Imprecise or missing bright stars

​

​

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===== Use with Skychart =====

===== Use with Skychart =====

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To solve the problem with the missing bright stars it not include any star present in Tycho2 catalog or any star brighter than magnitude 10. This implies you must always activate the Tycho2 at the same time with this catalog.

To solve the problem with the missing bright stars it not include any star present in Tycho2 catalog or any star brighter than magnitude 10. This implies you must always activate the Tycho2 at the same time with this catalog.

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To use this catalog start by getting the part you need from the [[en:​download ​catalogs]] page.\\

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To use this catalog start by getting the part you need from the [[en:​download]] page.\\

It is split in three part so you can get only the zone visible from your area.

It is split in three part so you can get only the zone visible from your area.

* ucac3-catalog-south.zip ​ : South zone -90 to -30

* ucac3-catalog-south.zip ​ : South zone -90 to -30

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* ucac3-catalog-north.zip ​ : North zone +22.5 to +90

* ucac3-catalog-north.zip ​ : North zone +22.5 to +90

A fourth file ucac3-index.zip contain the optional search index for all the zones.\\

A fourth file ucac3-index.zip contain the optional search index for all the zones.\\

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Each file is about 500MB is size.

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Each file is about 500 MB is size.

Extract all this zip under ciel\cat or share/​skychart/​cat. As each file is autonomous there is two common file on each, when prompted for replacement you can respond yes or no without effect.

Extract all this zip under ciel\cat or share/​skychart/​cat. As each file is autonomous there is two common file on each, when prompted for replacement you can respond yes or no without effect.

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Then from Skychart open the menu [[en:​documentation:​catalog|Setup -> Catalog]], click the **Add** button and select the file 3uc.hdr.\\

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Then from Skychart open the menu [[en:​documentation:​catalog|Setup -> Catalog]], click the **Add** button and select the file 3uc.hdr. ​Click on the first column to make it green\\

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Then open the [[en:​documentation:​catalog#​cdc_stars|Cdc Stars]] section to activate Tycho2 and disable the GSC

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Then open the [[en:​documentation:​catalog#​cdc_stars|Cdc Stars]] section to activate Tycho2 and disable the GSC. Do not forget to save the default options.

My preferred star catalog setting for general use is now:

My preferred star catalog setting for general use is now:

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| Tycho 2 | 0 - 6 | 0 - 45 |

| Tycho 2 | 0 - 6 | 0 - 45 |

| 3UC | 0 - 3 | 0 - 5 |

| 3UC | 0 - 3 | 0 - 5 |

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===== Build your own catalog =====

===== Build your own catalog =====

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If you have a copy of the UCAC3 DVD you can use Catgen to build your own catalog from the original data files. This allow you to include more or less information for each star depending on your needs.

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If you have a copy of the UCAC3 DVD, or if you can download the files from the [[ftp://​cdsarc.u-strasbg.fr/​pub/​cats/​I/​315/​|CDS]], ​you can use Catgen to build your own catalog from the original data files. This allow you to include more or less information for each star depending on your needs.

You must first convert the binary data on the DVD to ASCII text files using the include u3read program or my u3conv program.\\ ​

You must first convert the binary data on the DVD to ASCII text files using the include u3read program or my u3conv program.\\ ​

The advantage of u3conv is it process all the files at a time and add the star identifier and the color index after the other data. There is also a switch to filter or not the Tycho2 and bright stars.\\

The advantage of u3conv is it process all the files at a time and add the star identifier and the color index after the other data. There is also a switch to filter or not the Tycho2 and bright stars.\\

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You can download u3conv for [[http://​www.ap-i.net/​pub/​skychart/​ucac3/​u3conv.zip|Windows and Linux]] or get the [[http://​skychart.svn.sourceforge.net/​viewvc/​skychart/​trunk/​tools/​cat/​ucac3/​src/​|source code]]. Run the program in a console to show the syntax help.

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You can download u3conv for [[http://​www.ap-i.net/​pub/​skychart/​ucac3/​u3conv.zip|Windows and Linux]] or get the [[https://​skychart.svn.sourceforge.net/​svnroot/​skychart/​trunk/​tools/​cat/​ucac3/​src/​|source code]]. Run the program in a console to show the syntax help.

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Then use [[en:​documentation:​catgen|Catgen]] to convert the text files to a binary catalog optimized for chart display. You can start by loading the [[http://​skychart.svn.sourceforge.net/​viewvc/​skychart/​trunk/​tools/​cat/​ucac3/​|project file]] used for the standard catalog.\\

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Then use [[en:​documentation:​catgen|Catgen]] to convert the text files to a binary catalog optimized for chart display. You can start by loading the [[https://​skychart.svn.sourceforge.net/​svnroot/​skychart/​trunk/​tools/​cat/​ucac3/​ucac3_catalog.prj|project file]] used for the standard catalog.\\

Use a snapshot more recent than skychart-3.1-1232 as I correct a few bug with Catgen.

Use a snapshot more recent than skychart-3.1-1232 as I correct a few bug with Catgen.